Revised Ciprofloxacin Breakpoints for Salmonella: Is it Time to Write an Obituary?

• Published in: Journal of Clinical and Diagnostic Research
• Main Authors: Revathy Girish, Anil Kumar, Sadia Khan, Kavitha R. Dinesh, Shamsul Karim
• Format: Article
• Language: English
• Published: JCDR Research and Publications Private Limited 2013-11-01
• Subjects: salmonella typhi; salmonella paratyphi a; ciprofloxacin; resistance; breakpoints
• Online Access: https://jcdr.net/articles/PDF/3581/14-%207312_E(C)_F(T)_PF1(PP)_PFA(NC)_PF2(PP).pdf
• ISSN: 2249-782X; 0973-709X

Objectives: To determine the minimum inhibitory concentration of ciprofloxacin among 50 blood stream isolates of Salmonella enterica. Material and Methods: A total of 50 consecutive isolates of Salmonella enterica were tested for susceptibility to antimicrobials using the Kirby Bauer disk diffusion method. Minimum inhibitory concentrations were determined using Hi-Comb strips. All results were interpreted according to the CLSI guidelines. Results: Of the 50 isolates 70%were Salmonella Typhi, 4% Salmonella paratyphi A, 2% Salmonella paratyphi B and the remaining 10% were identified only as Salmonella species. Using the CLSI 2011 breakpoints for disc diffusion, 86% (43/50) were resistant to nalidixic acid(NA), 22% (11/50) to ciprofloxacin, 12% to azithromycin, 6% to cotrimoxazole, 4% to ampicillin and 1% to chloramphenicol. The MIC50 and MIC90 of ciprofloxacin for S.Typhi were 0.181 μg/mL and 5.06 μg/mL respectively. While the same for S. paratyphi A was 0.212μg/mL and 0.228μg/mL respectively. None of the isolates were multi drug resistant and all were susceptible to ceftriaxone. Using the CLSI 2012 revised ciprofloxacin breakpoints for disc diffusion (>31mm) & MIC (<0.06 μg/mL), 90% (45/50) of these isolates were found to be resistant. Conclusion: MIC’s of ciprofloxacin should be reported for all salmonella isolates and should be used to guide treatment. Blindly following western guidelines for a disease which is highly endemic in the subcontinent will spell the death knell of a cheap and effective drug in our armamentarium. Therefore it will be too premature to declare that “the concept of using ciprofloxacin in typhoid fever is dead!”